The present disclosure relates to methods and systems for producing fertilizer from organic waste and fertilizer compositions prepared by the same. In certain aspects, the present disclosure relates to methods and systems for preparing organic-based fertilizers (e.g., low nitrogen or high nitrogen fertilizers) in dry, water soluble and/or suspendible form, and fertilizer compositions prepared by the same. In some of the presently preferred aspects, the present disclosure relates to methods and systems for preparing high nitrogen content, organic-based fertilizers in dry, water soluble and/or suspendible form, and fertilizer compositions prepared by the same. The fertilizer compositions described herein may advantageously be used for agricultural applications, turf management applications, and others.
Organic waste material, such as food waste, can be converted into useful products or have useful products removed from it. Such methods of processing organic waste include microbic fermentation or digestion, in which microorganisms break down the waste material using biochemical processes.
Anaerobic fermentation involves four distinct stages. The first stage is bacterial hydrolysis in which insoluble molecules such as organic polymers, e.g., carbohydrates, fats, and proteins, are broken down into smaller, water-soluble subunits. The hydrolysis products include simple sugars, lipids, and amino acids that become available for other bacteria.
The second stage is acidogenesis, in which acidogenic bacteria convert the hydrolysis products into volatile fatty acids, which are short chain organic acids, the most important of which is acetic acid, as well as ammonia, hydrogen, and carbon dioxide. The third stage is acetogenesis, in which these bacteria convert the resulting organic acids into acetic acid and additional hydrogen and carbon dioxide. The fourth stage is methanogenesis in which methanogenic microorganisms convert the hydrogen and acetic acid to methane and carbon dioxide.
Commonly, ammonia gas produced by anaerobic fermentation is lost, for example, through volatilization when the anaerobic digestate is removed from the digestion vessel and exposed to atmosphere. Ammonia dissolved in waste water as ammonium ions is also lost in waste water removed from the digestate. The discharge of gaseous ammonia and/or liquid waste water containing ammonium ions can result in environmental and public health concerns. Even in cases where the ammonia is recovered as a waste product, e.g., by ammonia stripping, the loss of nitrogen content from the bio-digestate greatly diminishes its value as a fertilizer. Thus, there exists a need for an organic or organic-based fertilizer having a high nitrogen content. In addition, there exists a need for a fertilizer that can be produced in a substantially dry, water soluble/suspendible form.
Although the present invention is described herein primarily by way of reference to the preferred embodiments wherein the fertilizer product is prepared from an anaerobic digestate, the present system and method is also amenable to the preparation of a substantially dry, water soluble and/or suspendible fertilizer product from a digestate prepared by other types digestion processes, including aerobic digestion of organic materials and anoxic digestion of organic matter.
The present disclosure contemplates a new and improved apparatus, method, and fertilizer product that overcome the above-referenced problems and others.